The invention relates to a device enabling the contrast level of a video image to be regulated.
As is known from those skilled in the art, a highly contrasted video image area prevents both the details of which it is composed and the details which surround it from being seen clearly. It is then necessary to decrease the contrast level so as to make the details reappear.
In the case, for example, of the displaying of a video image on a television screen, the viewer has available a contrast-level adjustment. In the case in which one or more areas of the image are too highly contrasted compared to the rest of the image, the viewer can therefore act on the contrast control so as to decrease the contrast.
The contrast control is applied by means of an adjustment parameter acting on circuits enabling the level of the luminance signal (Y), the level of the blue color difference chrominance signal (CB) and the level of the red colour difference chrominance signal (CR) to be simultaneously adjusted. As a result of simultaneous application of the user adjustment control, the darkest areas of the image are then no longer contrasted enough. It is the details of which these darkest areas are composed which are no longer visible.
The invention does not have these drawbacks.